http://go-tour-jp.appspot.com/#24

gistfile1.txt

1.3351578377717581
1.4142135623730951
loop:4980, diff:0.01000, z:1.419186346344104 
1.419186346344104

Program exited.

go-tour-24.go

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z := 1.0
	for i := 0; i < 10; i++ {
		z = z - (z*z-x)/2*z
	}

	return z
}

func Sqrt2(x float64) float64 {
	z := 1.0
	bef := z
	lim := 0.01
	for i := 0; i < 10000; i++ {
		z = z - (z*z-x)/2*z
		// ifステートメント中の局所変数
		if diff := math.Abs(bef - z); diff < lim {
			fmt.Printf("loop:%v, diff:%.05f, z:%v \n", i, diff, z)
			return z
		} else {
			bef = z
		}
	}

	return z
}

func main() {
	fmt.Println(Sqrt(2))
	fmt.Println(math.Sqrt(2))
	fmt.Println(Sqrt2(2))
}